1. Field of Invention
The present invention relates to a billboard and control method thereof, and more particularly to a large stormproof billboard and control method thereof.
2. Description of Related Arts
Billboards are used as devices to transmit advertising information to the public, and according to different needs, the billboards can be made into various forms. Among that the large billboards which are established on transport corridors, transport hubs and so on are more common, the billboard stents of the billboards are usually supported on single column or multiple columns, and according to the billboard face, the billboards can be divided into single-faced, double-faced and multiple-faced. Because such billboards have simple structure, easy production process and can attract the attention of passers, the billboards are widely used. However, in actual use, it is found that: because the billboard stents fixed with the column and the billboard face to the public, the billboards can not change windward side with the wind direction after the billboards are set, so that the billboard may be damaged or fall down in bad weather, which does not only bring unnecessary loss to the advertisers and manufacturers, but also brings great security risk to the pedestrians. In order to eliminate such defects, it is tended to increase the size of the column, improve the material of the billboard stent and so on to meet the wind load in windy weather, but this program will obviously increase the manufacture cost of billboard.
Therefore, people design a stormproof billboard, such as a roadside stormproof billboard, according to Chinese patent, Publication No. CN2760701Y, this patent discloses that: an eccentric column is formed by a column and a billboard panel, the billboard panel connects with the column by a shaft lining so as to rotate with respect to each other, a turn restoration assembly is fixed with the billboard panel, the turn restoration assembly comprises two restoring springs symmetrically disposed on two sides of a support shore, two ends of each restoring spring respectively contact with a movable plate and a mounting plate, the top of the support shore fixed with a rotary block held between the two movable plates, two ends of the rotary block are cone. In use, under the wind force, the billboard panel rotates with respect to the column, drives rotary block and compresses the restoring springs to form a torque. When the wind force is reducing, under the force of the restoring springs, the billboard panel is reset, and the torque is released. Clearly, using such billboards can overcome the disadvantage of the conventional billboard to a certain extent. However, after analysing the structure carefully, it is found that: because the billboard panel always rotates with respect to the column and the billboard panel is located on a higher position, even if there is slightest wind, the billboard will rotate, namely, the billboard will deviate from the best direction; when the wind force is reducing, because the billboard panel is heavy, the restoring speed of the billboard panel is slow with only two springs, and when the wind direction changes in a larger scope, the billboard panel has a dead center and therefore can not complete the wide-angle turn. Therefore, in the use of the billboard panel, the billboard can not be in the best direction so that the advertising effectiveness is affected.
And as to an unloading method of the wind load on a billboard and an anti-wind billboard, according to Chinese patent, Publication No. CN100390838C, this patent discloses a control method of the billboard, which uses a wind speed sensor to measure real-time wind speed, an anemoscope translates the wind speed into an electronic control signal, a comparison circuit of the anemoscope compares the electronic control signal with a predetermined control parameter, a motor is controlled by a relay; the motor drives laminas of the louver style billboard panel to adjust an angle by a reduction device and a transmission mechanism. By using the above structure, the windward side of the billboard can be changed to a certain extent for unloading the wind load of the billboard. However, the billboard also has the following shortcoming: first, in control, the control system of the control method simply monitors the real-time wind speed, when the wind speed is greater than the security value and the wind direction is in parallel with the billboard, the system still sends the rotation signal to the laminas of the billboard, but this is unnecessary; and in the process of adjusting laminas angle, because the rigid mechanical drive always exists, the wind load is always transferred to the billboard stent. In bad weather, the wind speed is very unstable, in the process of adjusting laminas, if the wind speed increases instantaneously, the system can not make the corresponding adjustment, the billboard may be damaged by wind. Second, for the mechanical part, because of the louver structure, the movable parts are complex; and because the billboard panel is not a whole, advertise image must be sprayed or consists of plural screens, which makes the image effect bad, maintenance and replacement is also very troublesome.